In industrialized countries, urinary bladder cancer is the fourth most common malignancy in males, and the fifth most common neoplasm overall. The disease basically takes two different courses: one where patients have multiple recurrences of superficial tumors (Ta and T1), and one which progresses to a muscle invasive form (T2+) which can lead to metastasis. About 5-10% of patients with Ta tumors and 20-30% of the patients with T1 tumors will eventually develop a higher stage tumor (Wolf, H. et al. Bladder tumors treated natural history. Prog Clin Biol Res 221, 223-55 (1986).). Patients with superficial bladder tumors represent 75% of all bladder cancer patients. No approved clinically useful markers separating such patients by likelihood of progression exist.
It is believed that patients presenting isolated or concomitant carcinoma in situ (CIS) lesions have a higher risk of disease progression to a muscle invasive stage. The CIS lesions may have a widespread manifestation in the bladder (field disease) and are believed to be the most common precursors of invasive carcinomas (Spruck, C. H., et al. Two molecular pathways to transitional cell carcinoma of the bladder. Cancer Res, 54: 784-788, 1994; Rosin, M. P. et al. Partial allelotype of carcinoma in situ of the human bladder. Cancer Res, 55: 5213-5216, 1995). Generally, it is known that class T1 tumors have a higher risk of further progression than class Ta tumors. However, it is often difficult to differentiate Ta from T1 stage tumors, and the two stages are often confused. The ability to predict which tumors are likely to recur or progress would have great impact on the clinical management of patients with superficial disease, as it would be possible to treat high-risk patients more aggressively (e.g. with radical cystectomy or adjuvant therapy).
Although many prognostic markers have been investigated, the most important prognostic factors are still disease stage, dysplasia grade, and especially the presence of areas with CIS (Anderstrom, C., et al., The significance of lamina propria invasion on the prognosis of patients with bladder tumors. J Urol, 124: 23-26, 1980; Cummings, K. B. Carcinoma of the bladder: predictors. Cancer, 45: 1849-1855, 1980; Cheng, L. et al. Survival of patients with carcinoma in situ of the urinary bladder. Cancer, 85: 2469-2474, 1999.). The current standard for detection of CIS is urine cytology and histopathologic analysis of a set of selected site biopsies removed during routine cystoscopy examinations; however these procedures are not sufficiently sensitive. Implementing routine cystoscopy examinations with 5-ALA fluorescence imaging of the tumors and pre-cancerous lesions (CIS lesions and moderate dysplasia lesions) may increase the sensitivity of the procedure (Kriegmair, M. et al., Early clinical experience with 5-aminolevulinic acid for the photodynamic therapy of superficial bladder cancer. Br J Urol, 77: 667-671, 1996). However, this screening is not yet routine.
Monitoring of gene expression levels may be used to find markers whose elevated expression correlates either: with bladder cancer progression or death from bladder cancer; or, with no progression or death. Further, once such markers are found, one may combine the gene expression levels of such markers into sets or signatures, which, in combination, may indicate the likelihood of progression or death more reliably than when monitoring them separately.
Gene expression levels can be monitored by assaying a subject RNA using a method or process that detects a signal coming from the RNA molecules. Examples of methods or processes used to monitor gene expression include nucleic acid hybridization, quantitative polymerase chain reaction (or other nucleic acid replication reactions), nucleic acid sequencing, protein product detection, and visible light or ultra-violet light spectrophotometry or diffraction. Such methods can utilize fluorescent dyes, radioactive tracers, enzymatic reporters, chemical reaction products, or other means of reporting the amounts or concentrations of nucleic acid molecules. Gene expression levels can be monitored by first reverse transcribing the mRNA from a subject's sample to cDNA, then amplifying the cDNA using polymerase chain reaction (PCR).